Resp 3 Flashcards
Outward forces (mmHg)
Capillary 7;
Interstitial osmotic pressure 14;
Negative interstitial fluid pressure 8;
Total 29
Inward forces (mmHg)
Plasma protein osmotic pressure 28
Elevated PO2 levels are associated with
Increased O2 levels in the inhaled air;
Polycythemia
Decreased PO2 levels are associated with
Decreased O2 levels in air; Anemia; Heart decompensation; COPD; Restrictive pulm dz; Hypoventilation
The amount of gas dissolved in a solution is proportional to its partial pressure
Henry’s Law
Equation for dissolved oxygen in blood
PaO2 x 0.003
Diffusion of a gas is directly proportional to:
Pressure gradient, membrane area, & gas solubility
Diffusion of a gas is inversely proportional to:
Membrane thickness and square root of molecular weight
A-a gradient
PAO2 - PaO2. Difference b/w alveolar PO2 and arterial PO2
A-a gradient normal range for PO2 & PCO2
5-15 mmHg;
2-10 mmHg
Alveolar gas equation (calculates PAO2)
PAO2= PIO2 - PACO2/R R = resp quotient (0.8)
Hypoxemia d/t V/Q mismatch, diffusion block, or right-to-left shunt would effect A-a gradient how?
Increased
Hypoxemia d/t hypoventilation effects A-a gradient how?
Normal
Supplemental O2 is helpful in all causes of Hypoxemia except?
Right-to-left shunt
What form does iron carry O2?
Ferrous (Fe++)
O2 binding capacity of blood
20.1ml O2/100ml
O2 content of blood equation
O2 content = (O2 binding capacity x %Sat) + dissolved O2
Normally 1 g Hb can bind _____ ml O2
1.34
Cyanosis results when deoxygenated Hb _____
> 5g/100 ml
______ of arterial blood decreases as Hb falls, but _____ & _____ do not
O2 content;
O2 sat & arterial PO2
Arterial PO2 decreases w/ chronic lung dz b/c physiological shunt decreases _______
O2 extraction ratio
Causes defective O2 transport > low sat
methemoglobinemia
Causes of Methemoglobinemia?
Nitrites, benzocaine, metabolites of prilocaine
S/sx of cyanide poisoning
Tachycardia, hypotension, coma, acidosis, increased venous O2, rapid death
Tx of cyanide poisoning
sodium nitrite & amyl nitrites oxidize Hb to metHb which binds cyanide.
Thiosulfate binds this cyanide forming thiocynate which is excreted by kidneys
Cyanide blocks what enzyme that is needed for ATP?
Cytochrome oxidase
_________ is the driving force for the chemical reaction that creates oxyhemoglobin
O2 tension
P50
Indicates the partial pressure of oxygen required to achieve 50% of Hb saturation
Positive cooperativity
The sigmoid shape of oxygen-Hb curve that is a result of a change in affinity of Hb as each successive O2 molecule binds to a heme site